Composite digital logic microwave phase shifter

ABSTRACT

A microwave phase shifter comprising a strip transmission or meander line associated with a ferrimagnetic toroid or ferrimagnetic substrate divided into discrete operative regions. These discrete operative regions form the magnetic memory elements of a digital logic function. The device thus operates as a digitally controlled phase shifter in which the ferrimagnetic elements serve the dual purpose of operating on the digital control code signals as memory elements, while simultaneously effecting stage-by-stage phase shift of the microwave energy in the said meander line or strip-line.

United States Patent 1 Boensel COMPOSITE DIGITAL LOGIC MICROWAVE PHASESHIFTER [75] Inventor: Donald W. Boensel, La Canada,

Calif.

[73] Assignee: International Telephone and Telegraph Corporation, NewYork, N.Y.

[22] Filed: Dec. 2, 1970 [21] App]. No.: 94,510

[52] US. Cl. ..333/24.l, 333/84 M [51] Int. Cl. ..I-I0lp 1/32 [58] Fieldof Search ..333/24.l

[56] References Cited UNITED STATES PATENTS 3,478,283 11/1969 Simon eta1 ..333/24.l X 3,274,521 9/1966 Nourse ..333/24.1 3,332,042 7/1967Farris ..333/24.l X 3,371,293 2/1968 Jones et al ..333/24.1

3,418,605 12/1968 Hair etal ..333/24.l

Primary Examiner-Paul L. Gensler Attorney-C. Cornell Remsen, Jr., WalterJ. Baum, Paul W. l-lemminger, Charles L. Johnson, Jr. and

Thomas E. Kristofferson [57] ABSTRACT A microwave phase shiftercomprising a strip transmission or meander line associated with aferrimag netic toroid or ferrimagnetic substrate divided into discreteoperative regions. These discrete operative regions form the magneticmemory elements of a digital logic function. The device thus operates asa digitally controlled phase shifter in which the ferrimagnetic elementsserve the dual purpose of operating on the digital control code signalsas memory elements, while simultaneously effecting stage-by-stage phaseshift of the microwave energy in the said meander line or strip-line.

6 Claims, 4 Drawing Figures COMPOSITE DIGITAL LOGIC MICROWAVE PHASESI'IIFTER BACKGROUND OF THE INVENTION 1. Field of The Invention Thepresent invention relates to radio frequency phase shifters, and moreparticularly, to microwave phase shifters which are digitallycontrollable.

2. Description of The Prior Art In the prior art there have been anumber of microwave phase shifters developed and produced for particularapplications. Among the mechanically operated versions are the so-calledvariable a dimension waveguide, the rotary waveguide phase shifter, thehelical-line trombone phase shifter, and many others.

In the field of electrically controlled phase shifters, the genericcategory to which the present invention belongs, there may be found bothanalog and digitally controlled devices. A very complete and currentreference describing the state of this art, in particular relation tothe more immediate background of the present invention, is RadarHandbook by Merrill I. Skolnik, a McGraw Hill book, (1970). Inparticular, Chapter 12 of that reference discusses the theory andvarious structures for electrically controllable phase shifters. Theterm ferrimagnetic, as it applies to materials of the families of bothferrites and garnets (magnetic ceramics) is extensively used in thepresent application. The definitions and description of thecharacteristics of those materials contained in the aforementionedreference are pertinent to the present invention, and the meaning ofterms used herein, which are also found in that reference, are the same.

The so-called Reggia-Spencer phase shifter shown in the reference is aprime example of a high powered inherently analog type controllablephase shifter mounted within a waveguide. Other types of digital andanalog shifters all employing transmission lines of one type or another,are discussed.

The reference also shows and describes strip-transmission-line,slow-wave phase shifters using the socalled meander line. In thatparticular prior art device, ferrite elements in the form of hollowrectangular guides envelop the meander line which is emplaced as thecenter conductor strip of a transmission line. The ferrite element isbroken into discrete lengths axially and these are subject to control bylatching wires. That prior art structure is adaptable to digital controlof the phase shift from the outputs of an external digital device, suchas a multibit digital shift register or memory device connected thereto.Thus the source of digital control would be separate except for theinterconnection wires.

One important disadvantage of these prior art and digital type phaseshifters structures, has been the size and amount of equipment involvedto accomplish the objective. The manner in which the present inventioncontributes to this art in providing a more economical, simpler and morereliable structure will be seen as this description proceeds.

SUMMARY OF THE INVENTION It may be said to have been the principalobject of the present invention to develop a composite digital logicmicrowave phase shifter, controllable and combining the magnetic memorymedia of the shift register digital control device with theferrimagnetic material used in connection with a strip or meander linefor the actual control of phase shift of a microwave signal through thetransmission line.

The preferred instrumentation of the present invention involves a seriesof discrete phase shifter stages constructed of microwave strip onferrite substrates. The devices are nonreciprocal and are actuated byswitching the material between a positive and a negative state of fluxsaturation.

Alternatively, the structure may involve a ferrimagnetic toroidarrangement in connection with a symmetrical strip-line, although themeander line on a ferrimagnetic substrate produces the most compact andpractical structure in low and moderate power situations.

Separation of the line into n digital stages is accomplished either byphysical separation, barrier techniques or actual division of theferrite substrate into independent platelets. Thus, each stagecorresponds to a region of the magnetic ceramic substrate and operatesdiscretely to provide a predetermined phase shift. The meander linetraverses all of the said regions, and therefore, the total phase shiftthrough the meander line is equal to the sum of the shifts provided inthe individual stages. Since the said regions each serve the dualpurpose of influencing the corresponding meander line section to producephase shift and also acting as, for example, the digital memory in aserially operated shift register arrangement, each successive region isconstructed to provide double the phase shift provided by the precedingstage (a standard digital 'bit progressive significance). While thestructure of a shift register has been selected as the logicalconfiguration for detailed description hereinafter, it is to beunderstood that generalized digital logic functional circuitry isinstrumentable alternatively and with equal ease. For example, ratherthan operating as a shift register, the design could be such as to makethe logic combination operable as a counter (accumulator),an adder,digital comparator, or other arrangement.

In the configuration to be described, the first stage, corresponding tothe least significant digit, provides 22 A" phase shift. A four-bitembodiment, as is illustrated herein and to be discussed in detailhereinafter, provides 45, and in the second through fourth stages.

Externally provided digital control pulses and shift pulseseffect-operation of the specific aforementioned overall device, andsince the phase shift provided by each succeeding digital stage isgreater, the length of meander line affected increases in eachsucceeding (more significant) stage. Referring again to theaforementioned Radar Handbook reference, the device depicted on page l223, FIG. 19, illustrates a comparable situation (in that particulardetail only) in that the ferrimagnetic materials sections are ofprogressively variable size.

The definitions, materials selection criteria, and other considerationssuch as power handling capability, magnetostriction and temperaturestabilization, etc., as set forth in Chapter l2 I of the aforementionedreference, are all pertinent to the detailed design of a structureaccording to the present invention.

A more detailed description of one embodiment of the present invention,taken with the drawings, follows hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a circuit for aninstrumentation of the present invention in the meander line and ferritesubstrate form.

FIG. 2 is a functional waveform chart, including both electrical pulserelationships and magnetic condition relationships.

FIG. 3 is a cross-section detail illustrating the manner ofinstrumenting individual phase shift regions of the present invention ina symmetrical strip transmission line using a ferrim agnetic toroid.

FIG. 4 is a typical microstrip meander line phaser stage where themeander line is on a flat ferrimagnetic platelet. This figure alsoillustrates flat toroidal material geometry typically.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to FIGS. 1and 2, the waveforms of FIG. 2 will be identified and related to FIG. 1.

At the outset it will be observed that although a fourbit logic andphase shift configuration is illustrated in FIG. 1, it was considerednecessary to depict only the first three stages insofar as the waveformsof FIG. 2 are concerned.

The first line, I, on FIG. 2, depicts the transfer (shift) signal fed tothe B windings 10, 13, 16 and 19 in FIG. 1. The second line of FIG. 2depicts the somewhat delayed current pulse I fed to the A winding at 9for the first stage of the overall circuit.

The ferrimagnetic regions represented by 5, 6, 7 and 8 will be generallyreferred to as the identifications for the 4 stages of the overallfour-bit device. Accordingly, the currents I I, and I:, are the Cwinding output current pulses from 11, 14 and 17, respectively.Similarly, I I, and I are the comparable currents after passage throughthe intervening delay circuits. These currents 1,, I, and I, passthrough windings l2, l and 18, respectively, and as such, preset theshifting action effected by I,.

Between stages 5 and 6 it will be noted that the interconnections from11 to 12 include a diode 22, capacitor 23 and resistor 24. The diode 22insures that the priming action or the set-up" of the succeeding stageeffected by C winding output pulses in each case, is unilateral, so thatno reverse interaction is extant.

The capacitor 23 and resistor 24 act as a delay filter affecting thepulse shape, as well as delaying the succeeding A winding currentpulses, was will be seen in FIG. 2. The function of diodes 25 and 28 areanalogous to diode 22, and similarly, capacitors 26 and 29 performfunctions analogous to that of capacitor 23. Obviously, also resistors27 and 30 perform the same function between stages 6 and 7 and 7 and 8,respectively as performed by resistor 24 between stages 5 and 6. Thetotal meander line comprises the sections 1, 2, 3 and 4, which are shownin substantially the same length in FIG. I for convenience. It is to beunderstood however, that stages producing the larger incremental phaseshift A dz, would normally be constructed with longer sections ofmeander line. This follows from the previous discussion of least andmost significant digital stages and their respective incrementalcontributions to the overall phase shift. The microwave signal input tothe meander line circuit begins at 20, the output being depicted at 21.

In FIG. 2, the lines 1, and d), and will be seen to depict the magneticlatched condition of either d or 4),. In each case, the conditionsdepicted on these last three lines of FIG. 2 are arbitrarily selectedbut are consistent with the controlling current pulse waveforms above inFIG. 2. From this showing it will be understood that the respective fluxor saturation states may be caused to shift from left to right, thepattern being incremented one position with each clock pulse, I,. Atthis point, it will also be realized that, since the square-loopferrimagnetic material latches, the currents that produce the changesneed not be sustained, and accordingly, in the absence of furtherpulsing, will remain in their last condition. The foregoing follows fromthe known characteristics of latching type (square-hysteresis-loop)retentive materials extant in this art.

The meander line and ferrimagnetic substrate device of FIG. 1 isinherently nonreciprocal.

The convention assumed for the purpose of explanation is that a positivestate of magnetic material saturation (plus 41),) produces a phase shiftof Ad) equals 0, where 0 is 22 It", for example. Similarly, the second,third and fourth stages 6, 7 and 8, respectively, produce 20, 40 and 80,respectively. It is also assumed in the understanding of FIG. 1, takenwith FIG. 2, that current, or current pulse flowing into the dots willset the magnetic material in the condition. A change from 4:, to (I),will produce a current flow out of the dot of the corresponding Cwinding in each case. As previously discussed, C winding output currentsare delayed for purposes already obvious from the previous discussion.Accordingly, it will be understood that the ferrimagnetic materialsaturation condition is switched so that the states of flux shift fromleft to right, the pattern being incremented one position with eachclock pulse I, (a normal shift register function).

Referring now to FIG. 3, one form of arrangement by which theferrimagnetic material cooperates with a transmission line structure toproduce the effects in each of the stages, is shown. The detailstructure of FIG. 3 is known and used with a single latching wire(typically 9) as an externally controlled element in a digital phaseshifting system of a prior art type. A socalled symmetrical strip-lineis illustrated in cross-sec tion in FIG. 3, the center conductor 36being placed between two ground planes 30 and 31. The ferrimagnetictoroid 34 is held in its position against the edge of the centerconductor strip 36 and is insulatingly emplaced symmetrically betweenthe said two ground planes by insulating members 32 and 33. Theseinsulating materials 32 and 33 may be foamed plastic or other known lowloss microwave transmission line insulating material. Two magnetizingwires 9 and 11 are shown as they might correspond to A and C windings ofa typical stage in FIG. 1. Similarly, an orthogonally placed magneticexcitation wire (winding) is illustrated at 10. The wire 10 could beregarded as corresponding to a B type winding in a given stage. A fluxpath indicating arrow is shown M35 as it relates to the field producedby 9 and 11.

Referring now to FIG. 4, a flat toroid configuration is shown for anunderstanding of the general form required for a discrete meander lineferrimagnetic region, such as one of those depicted at 5, 6, 7 or 8 inFIG. 1. The meander line itself is shown at 41, lying on theferrimagnetic substrate 40. The latching wire 9 may actually be twoindependent windings, in effect, and would be a typical placement for Aand C windings (as schematically depicted in FIG. 1). The line 10,although not truly orthogonal, in its magnetic effect, is located tominimize interaction with the lines at 9 and 11. The flux arrow 44indicates a type of circular field polarization, which is of itselfknown and corresponds to one of the theories discussed in theaforementioned Radar Handbook concerning the interaction of theferrimagnetic material and the meander or strip-line with which itcooperates, to produce the phase shift effect.

From an understanding of the nature of the present invention, variousmodifications and variations will suggest themselves to those skilled inthis art. Different ways of producing the interstage delay are, ofcourse, readily possible. To mention one additional possible variation,it will be realized that the B windings of FIG. 1 might be isolated bymeans of electrical circuitry connected in the series path between themobviating the requirement that the B fields be located orthogonallyoriented to avoid interactions with the other windings. The basicfunctioning of the system insofar as the phase shifting effect ofmagnetic saturation in the ferrimagnetic substrate is concerned, is notdependent on the exact orientation of the granular structure of themagnetic material itself or on the exact magnetization vectors applied.The factors relating to orientation of magnetic fields are alsodiscussed as a matter of prior art knowledge in the aforementioned RadarHandbook reference.

Accordingly, it is to be understood that the drawings and descriptionherewith presented are to be regarded as typical and illustrative andnot as limiting the scope of the present invention.

What is claimed is:

l. A latching multi-stage digital microwave phase shifter in which themicrowave phase influencing ferrimagnetic material is also used toregister the digital control signals, comprising:

an electromagnetic energy transmission line associated with saidferrimagnetic material, said line being divided and arranged into aplurality of serial stages each including an independent operativelyassociated magnetically responsive region of said ferrimagneticmaterial, to introduce a phase shift of the microwave energy flowing insaid transmission line which is the sum of the individual phase shiftsprovided by each of said stages, said stages each providing a discretecorresponding phase shift in accordance with one of first and secondmagnetic conditions of the corresponding magnetically responsive region;

means for applying externally generated first control pulses to a firstinput of the first of said stages in a direction to produce said firstmagnetic condition in the corresponding region of said first stage;

means comprising interstage coupling means for applying interstagecontrol pulses delayed with respect to said first control pulses to eachsucceedmg stage from each stage exhibiting said first magnetic conditionat any time, thereby to provide for operation of said serial stages as adigital logic circuit, the magnetic conditions of the said stagesproviding a corresponding phase shift through said transmission line;

and means for applying a magnetic flux transfer pulse at a second inputto all of said stages substantially contemporaneously, said transferpulses operating to transfer said first magnetic condition from each ofsaid stages in said first condition at any time to the following stage.

2. Apparatus according to claim 1, in which said transmission line is abalanced strip type line having a center conductor symmetrically spacedbetween two ground planes, said ferrimagnetic material is in the form ofa ferrimagnetic toroid for each of said stages insulatingly mountedbetween said ground planes and in lateral juxtaposition with said centerconductor.

3. Apparatus according to claim 1 in which said transmission lineincludes a meander line on a ferrimagnetic substrate and saidindependent regions are formed therein by separation of said substrateinto discrete ferrimagnetic platelets.

4. Apparatus according to claim 1 in which said transmission lineincludes a meander line on a ferrimagnetic substrate and saidindependent regions are formed therein by physical isolation betweenregions to provide substantial magnetic isolation.

5. Apparatus according to claim 4 in which said digital logic circuit isa shift register circuit comprising input and output windings associatedwith each of said independent regions of said stages for applying saidexternally generated first control pulses and for passing saidinterstage control pulses on to the next stage, respectively, each ofsaid stages also including a transfer winding arranged to form amagnetic flux substantially orthogonal with said input and outputwindings to minimize interaction, and in which means are included forconnecting said transfer windings for all of said stages in series.

6. Apparatus according to claim 5 in which said interstage couplingmeans includes an RC delay network and diode means connected betweensaid output winding of each of said stages and said input winding of thenext stage, thereby to apply said delayed interstage control pulses tosaid next stage input winding.

III i i

1. A latching multi-stage digital microwave phase shifter in which themicrowave phase influencing ferrimagnetic material is also used toregister the digital control signals, comprising: an electromagneticenergy transmission line associated with said ferrimagnetic material,said line being divided and arranged into a plurality of serial stageseach including an independent operatively associated magneticallyresponsive region of said ferrimagnetic material, to introduce a phaseshift of the microwave energy flowing in said transmission line which isthe sum of the individual phase shifts provided by each of said stages,said stages each providing a discrete corresponding phase shift inaccordance with one of first and second magnetic conditions of thecorresponding magnetically responsive region; means for applyingexternally generated first control pulses to a first input of the firstof said stages in a direction to produce said first magnetic conditionin the corresponding region of said first stage; means comprisinginterstage coupling means for applying interstage control pulses delayedwith respect to said first control pulses to each succeeding stage fromeach stage exhibiting said first magnetic condition at any time, therebyto provide for operation of said serial stages as a digital logiccircuit, the magnetic conditions of the said stages providing acorresponding phase shift through said transmission line; and means forapplying a magnetic flux transfer pulse at a second input to all of saidstages substantially contemporaneously, said transfer pulses operatingto transfer said first magnetic condition from each of said stages insaid first condition at any time to the following stage.
 2. Apparatusaccording to claim 1, in which said transmission line is a balancedstrip type line having a center conductor symmetrically spaced betweentwo ground planes, said ferrimagnetic material is in the form of aferrimagnetic toroid for each of said stages insulatingly mountedbetween said ground planes and in lateral juxtaposition with said centerconductor.
 3. Apparatus according to claim 1 in which said transmissionline includes a meander line on a ferrimagnetic substrate and saidindependent regions are formed therein by separation of said substrateinto discrete ferrimagnetic platelets.
 4. Apparatus according to claim 1in which said transmission line includes a meander line on aferrimagnetic substrate and said independent regions are formed thereinby physical isolation between regions to provide substantial magneticisolation.
 5. Apparatus according to claim 4 in which said digital logiccircuit is a shift register circuit comprising input and output windingsassociated with each of said independent regions of said stages forapplying said externally generated first control pulses and for passingsaid interstage control pulses on to the next stage, respectively, eachof said stages also including a transfer winding arrangeD to form amagnetic flux substantially orthogonal with said input and outputwindings to minimize interaction, and in which means are included forconnecting said transfer windings for all of said stages in series. 6.Apparatus according to claim 5 in which said interstage coupling meansincludes an RC delay network and diode means connected between saidoutput winding of each of said stages and said input winding of the nextstage, thereby to apply said delayed interstage control pulses to saidnext stage input winding.